Better parity with continuous limits

Author: teunbrand

R/scale-discrete-.R

@@ -19,8 +19,9 @@
 #' @param continuous.limits One of:
 #'   * `NULL` to use the default scale range
 #'   * A numeric vector of length two providing a display range for the scale.
-#'   * A function that accepts the existing continuous limits and returns a
-#'     numeric vector of length two.
+#'   Use `NA` to refer to the existing minimum or maximum.
+#'   * A function that accepts the limits and returns a numeric vector of
+#'   length two.
 #' @rdname scale_discrete
 #' @family position scales
 #' @seealso

R/scale-expansion.R

@@ -180,8 +180,7 @@ expand_limits_discrete <- function(limits, expand = expansion(0, 0), coord_limit
     check_numeric(continuous_limits, arg = "continuous.limits")
     check_length(continuous_limits, 2L, arg = "continuous.limits")
     missing <- is.na(continuous_limits)
-    limits       <- range(ifelse(missing, limits, continuous_limits))
-    coord_limits <- range(ifelse(missing, coord_limits, continuous_limits))
+    limits  <- ifelse(missing, range(limits), continuous_limits)
   }
 
   limit_info <- expand_limits_discrete_trans(